Drilling apparatus



June 30, 1942. w. w. PAGET DRILLING APPARATUS Filed March 5, 1940 4 Sheets-Sheet l l l .lillil r w N S A June 30, 1942. w. w. PAGET DRILLING APPARATUS Filed March 5, 1940 4 Sheets-Sheet 2 .IEW/III] f 15h/m20?? 072'22 ZJ ayeZ, l 0M wwwmay June 30, 1942. w. w. PAGET 2,288,543

DRILLING APFARATUS Filed March 5, 1940 4 Sheets-Sheet 5 v /08 /09 173g!! 2 1kg/3.

n wirf/Aw r f 1223062120@ (1)272/ Zd. Waye.

June 30, 1942- w. w. PAGET 2,288,543

DRILLING APPARATUS Filed March 5, 1940 4 Sheets-Sheet 4 Egg. 13.

Moronwrrcn DRILLING MoroR FEED CYLNDER /OlI 40 H2 '53 l2 l* 99 6 /29 95 ToRQuE CoNTRoLLED VALVE l 94 T-SUDE VALVE EXHAUST v To DRILL BIT 13u/en for: Zdv'u Zl/.Palge i'.

(Izzy.

Patented June 30, 1942 UNITED STATE DRILLING APPARATUS Win W. Paget, Michigan City,

Sullivan Machinery Company,

Massachusetts Ind., assixnor to a corporation of Application March 5, 1940, Serial No. 322,267

(Cl. Z55-47) 27 Claims.

This invention relates to drilling apparatus, and more particularly to improvements in rotary drilling apparatus of the high speed type especially designed for use in boring holes in relatively hard material such as hard rock or the like.

An object of this invention is to provide an improved drilling apparatus. Another object is to provide an improved drilling apparatus having improved feeding means and improved means for controlling the feeding means. A further object is to provide an improved fluid actuated feeding means for a rotary drilling apparatus, and means responsive to the resistance to drill bit rotation for automatically controlling the feeding pressure. Yet another object is to provide an improved fluid actuated feeding means having an improved means for controlling the flow of actuating fluid to and the venting of fluid from said feeding means. Another object is to provide an improved rotary drilling apparatus of the high speed type having improved means for automatically controlling the feeding pressure on the drill bit so as to maintain an automatically controlled and limited feeding pressure during the drilling operation. A further object is to provide an lmproved feed controlling means which has different degrees of responsiveness to different degrees of resistance to drill bit rotation whereby different feed controlling functions may be effected. Still another object is to provide an improved feed controlling means responsive to the resistance to drill bit rotation for regulating the flow of actuating pressure to the feeding means within predetermined degrees of resistance to drill bit rotation and for interrupting such flow when the resistance to drill .bit rotation reaches a predetermined point, and embodying means for automatically venting the feeding pressure when such point is exceeded. A still further object is to provide an improved feed controlling means for automatically interrupting the forward feed when the torque on the 'drill bit rotating motor reaches a predetermined point, and embodying means for venting the forward feeding pressure when such torque becomes excessive. A still further object is to provide an improved torquecontrolled valve means responsive to torque variations resulting from changes in load on the drill bit rotating motor for automatically controlling the feeding means. Another object is to provide an improved automatic feed controlling means whereby manual feeding of the drill may at any time during the drilling operation, and without any manipulation of transfer mechanism, supersede the automatic feeding operation.

A still further object is to provide an improved manual drill feed operating means associated with the fluid actuated feeding means whereby manual feed of the drill bit may be instituted at any time, at will, during the drilling operation and automatically interrupt feed by the fluid actuated feeding means, and having improved control means whereby when an excessive load is applied to the bit rotating motor by the manual feeding means the'fluid in the fluid actuated feeding means is automatically vented. Another object is to provide an improved automatic feed controlling means whereby manual control of the feed effecting elements may be initiated at any time during the operation of the automatic feeding devices simply by commencing to operate the manual feed effecting means, and whereby instantly upon the cessation of operation of the manual devices automatically con trolled feed will be automatically resumed. A still further object is to provide an improved manual drill feed operating means associated with automatic fluid actuated feeding means whereby the drill bit may be manually fed at will during the drilling operation and the operation of the automatic fluid actuated feeding means be automatically resumed when manual feed is discontinued, A still further object is to provide in combination with fluid actuated feeding means having automatic control of the supply of fluid feeding medium, an improved manual feed operating means, and to provide in the control means devices whereby when an excessive load is applied to the drill bit rotating motor through the manual feeding means the fluid feeding medium may be automatically vented. Another object is to provide for a drilling motor improved selectively operable manual and automatic feeding systems each utilizing in a common chamber a body of fluid feeding medium for the transmission to the drilling motor of a feeding pressure, and providing means whereby during the operation of one of said feeding systems automatic control of fluid feeding medium supply is accomplished and during operation of the other automatic control of fluid feeding medium ventlng is accomplished. Still another object is to provide an improved drilling apparatus embodying mechanism utilizing a fluid medium for the transmission of feeding pressures to the drilling motor and including means for selectively effecting manual or automatic feed, and means responsive to the resistance to drill bit rotation under either condition for regulating the volume of the fluid feeding medium. These and other objects and advantages the invention will,

' however, hereinafter more fully appear.

In the accompanying drawings there is: shown for purposes of illustration one form which the invention may assume in practice.

'i i these drawing-ism Figs. and when taken together, consti tute a view in longitudir l section through an illustrati' embodiment the proved drilling app 3 is" an enlarge. online Fig. 2.

Fig'. e is an enlarged cross sectional view' taken substantially on line of Fig. 1.

Fig. 5 is an enlarged cross sectional view taken substantially on line of Fig', l.

Fig. 6 is a detail view in longitudinal vertical section taken substantially on line 5 6 of Fig. 5.

Fig. 'l is a detail sectional view taken substantially on line l--l of Fig. 4.

Fig. 3 is a detail sectional view taken substantially on line 8-8 of Fig. 4l.

Fig. 9 is an enlarged detail sectional view taken in the plane of Fig. i, showing the torque-controlled valve means in a different position.

Fig. 10 is an enlarged detail sectional view taken substantially on line ill-i t of Fig. 8, showing the torque-controlled valve means in venting position.

Fig. 1l is an enlarged detail sectional view taken substantially on line li-li of Fig, fl.

Fig. 12 is a detail sectional view taken on line I2-I2 of Fig. 4, with parts shown in full.

Fig. 13 is a fragmentary sectional View taken in the plane of Fig. l2. showing the control valve in a different position.

Fig. le is a cross, sectional View taken on line ifi-dii of Fig. 12.

Fig. l5 is an enlarged horizontal detail view taken on line lil-l 5 of Fig. l.

Fig. 16 is a cross sectional view taken on line li-ifi of Fig. l5.

Fig. 17 is a cross sectional view taken on line ii--l'l of Figl5.

Fig. 18 is a diagrammatic View illustrating the fluid system and control means.

The present invention is an improvement over that disclosed in my copending application Serial No. 268,792, filed April 19, 1939, In my earlier filed application I disclose mechanism including coacting cylinder and piston elements for effecting pressure fluid operated forward feed of a bit rotating motor under automatic torque control and for effecting pressure fluid operated retraction of the bit rotating motor, together with manual means for bodily advancing and retracting the bit rotating motor and its pressure uid operated feeding means. With such a mechanism, when it is desired to utilize the manual feeding means to reposition the parts of the pressure fluid operated feeding devices to extend the feed eifectible by the latter it is necessary to reverse the manual control valve whose position determines the direction of relative movement between the elements of the pressure fluid operated feeding mechanism. In the normal mode of operation of such a structure the fluid actuated feeding means is first operated until it completes its forward feeding stroke. The feed piston of the Iiuid actuated feeding means is then retracted, and thereafter the manual feeding means is operated to feed the feed cylinder and the feed piston, both, of the fluid actuated feeding means into a new feeding position, and finally the fluid actuated feeding cross sectional view teiten i2 likewise suitably secured to the cylinder.

agences means is again operated to eect another forward feeding operation. With the mechanism illustrated in this present application, as will be duly pointed out, it is unnecessary to effect a retraction of the feed piston relative to the feed cylinder in order to provide for extension of the pressure fluid operated feeding of the bit rotating" motor, and improved means is provided whereby, within. the range permitted by the apparatus, the manual feeding means may be oper" ated at any time at will while drilling is going on automatically to discontinue the normal pressure fluid operated feeding operation and to effect a readjustment of the parts of the feeding devices, while drilling continues, without any manipulation whatever of the main manual feed control valve.'

In the illustrative embodiment, of the invention herein disclosed there is shown a rotary drilling apparatus of the high speed type especially designed for use in drilling hard rock or the like and adapted to use with core or plug abrasive type bits commonly known as diamond bits. The drilling apparatus as a whole comprises bit rotating means generally designated l, bit feeding means generally designated 2 and drill guiding and supporting means generally designated 3. The drill supporting and guiding means 3 is similar to that shown in said copending application and comprises a trunnion support 6 having a swivel plate 5 adapted to be secured in the saddle mounting of a conventional rock drill support.

The feeding means 2 likewise is similar to that shown in the copending application aforesaid and comprises a reciprocable feed cylinder d slidably guided in a bore l' in the trunnion support and containing a reciprocable feed piston t having a tubular piston rod 9 extending forwardly through packing; i@ carried by the front head il of the feed cylinder. The cylinder head i i is suitably secured to the feed cylinder and closes the front end of the cylinder bore, While the rear end of the cylinder bore is closed by a rear cylinder head The front and rear cylinder heads are engageable with the end surfaces of the trunnion support d to limit reciprocable movement of the feed cylinder in the trunnion support bore. Secured to the front end of the feed piston rod 9 is a head member lil. The feed piston 8 is double acting and has packings lil sealingly engaging the walls of the cylinder bore and secured in position by the members i5 and i6 in turn held in position on the rearward portion of the piston rod between a shoulder i1 and a detachable end plate i8, the latter secured as by screws I9 to the piston rod. Secured within the trunnion support 4 is a tube 20 having its axis arranged in parallelism with the feed cylinder axis, and extending longitudinally through this tube and rotatably mounted in depending bosses integral with the front and rear cylinder heads II and I2 is a tube 2|, the latter having formed along a portion of the length thereof screw threads 22 coacting with lthe threads of a non-rotatable feed nut 23. nut 23 is secured at 24 Within the trunnion suptively, the latter der head Il. The feed screw tube 2| extends rearwardly through a bore 21 in the rear cylinder secured to the front feed cylini tary motor 40 herein a head boss, as shown in Fig. 2, and has secured thereto a hand crank 28 having a grasping portion 29. Carried by the hand crank 28 is a spring-pressed plunger lock 30 having an operating handle 3| and engageable within a locking recess 32 in the rear cylinder head for locking the feed screw tube 2| against rotation during automatic feeding of the drill, as will later be ex-l plained.

As above mentioned, the forward end of the feed piston rod 9 supports the head member I3 (Fig. 1), and secured as by screws to the head member is a control head 35. Threadedly secured at 36 within this control head is a member 31 having a sleeve portion fitting within the bore of the feed screw tube 2| at the forward end of the latter, and secured as by welding at 38 to this sleeve portion is a tube 39 extending centrally within and in telescopic relation with the feed screw tube 2|, in the manner shown in Figs. 1 and 2. The tube 39 has a sliding fit with the walls of the bore of the tube 2| and serves to maintain the feed cylinder against rotation within its bore on the trunnion support, and in effect acts as a lateral sliding guide for the drill.

The drill bit rotating means I comprises a rohigh speed electric motor type comprising a stator casing 4I provided with front and rear heads 42 and 43, the motor parts being held in assembled relation by tie bolts 44. The motor has a usual field 45 and an armature rotor 46, the shaft 41 of the rotor being journaled in bearings suitably supported in the motor heads. head 43 has a rearward cylindric projection 48 mounted for limited rotation in ball bearings 49 supported within a bore formed in the control head 35. The bearings are retained in the control head bore by means of a retaining ring 50 secured as by screws I to the control head, and the cylindric projection is held against axial displacement with respect to its bearings by means of an end plate 52 secured as by screws to the projection 49. Electric energy may be conducted to the bit rotating motor 40 from any convenient source through a conventional connector plug 53 mounted on the control head 35 and connected through wiring 54 to the motor field 45, and a switch 55 is arranged in a chamber 56 in the control head for effecting starting and stopping of the motor in the manner fully described in the copending application above referred to. Suitably secured to the forward end of the motor rotor shaft is a chuck 51 which receives the supporting means for the drill rod which carries the drill bit. The purpose of the rotary mounting for the motor will be later explained.

Now referring to the means for supplying liquid under pressure to the hydraulic feeding means, it will be noted that formed in the control head 35 is a liquid supply chamber 60 to which liquid under pressuremay be conducted through a strainer 6I from a supply passage 62 formed in a head member 63 secured as by bolts to the control head 35. A supply connection 64 (Fig. 16) is adapted to supply liquid under pressure to the passage 62 from any suitable source. Also formed in the control head is a longitudinal bore 65 having arranged thereiny a ported valve bushing 66 in which a control valve 61 is reciprocably mounted. This valve is of the sliding spool type and is held against rotation within the valve bushing bore by a pin 68 arranged in a transverse bore in the valve stem 69 and having its ends guided in longitudinal guide slots in the member 31.

of the totally enclosed The rear motor' Also arranged in a transverse bore in the valve stem is a pin 1| having its ends projecting within an annular groove 12 in a rotatable member 13. This rotatable member has an integral valve adjusting screw 14 threadedly engaging a non-rotatable nut 'I5 formed Within the sleeve portion of the member 31. The screw 14 is rigidly secured at 16 to a tube 11, this tube extending centrally within the tube 39 and being square in cross section and having telescopically arranged within its bore a square control rod 18 (Fig. 3). This rod extends rearwardly from within the feed screw tube 2| and is secured at 19 (Fig. 2) to a rotatable member having a control handle 8|. The rotatable member 80 is rotatably mounted within the bore of the tube 2| at the rear end of the latter and is held in position therein by a retaining pin 82 secured within the hub of thev handle 28 and passing through an annular groove 83 in the member 80. It will thus be seen that by rotating the handle 8l the control valve 61 may be moved axially within the valve bushing bore through the rotatable screw 14 engaging the non-rotatable nut 15 integral with the member 31 and by the provision of the telescopically arranged square tube and rod the screw 14 may be rotated irrespective of the position of the control head relative to the trunnion support. Communicating with the rear end of the bore of the valve bushing is an exhaust chamber 85 connected by a passage 86 (Fig. 12) with an arcuate groove 81 in the head member 63 which in turn communicates with an exhaust passage 88 connected to atmosphere through an exhaust port 89 (Fig. 16). Surrounding the valve bushing are grooves 90 and 9| connected by ports with the valve bushing bore. A supply chamber 92 also communicates through ports with the valve bushing bore, while communicating with the front end of the valve bushing bore is an exhaust chamber 93, and a passage 94, controlled by a reverse-flow-preventing check valve 95, connects this exhaust chamber with the exhaust passage 88. The groove 9| is connected by a passage 96 in the control head with a passage 91 in the head plate I3, the latter passage communicating with the interior of the feed piston rod 9. Ports 98 (Fig. 2) connect the interior of the feed piston rod with the feed cylinder bore at the front side of the feed piston 8. Liquid under pressure may be supplied to the feed cylinder bore at the rear side of the feed piston from the supply chamber 92 through a passage 99, past a torquecontrolled valve means generally designated |00, to a forward feed passage |0I communicating with a passage |02 in the head plate I3. The passage |02 connects the passage |0I with a recess |03 which is in turn connected by a liquid conducting tube I04 extending centrally rearwardly through the feed piston rod Within the rear end of the feed cylinder bore at the rear side of the feed piston. The piston carries a packing |04' which sealingly engages the tube to prevent leakage. When the control valve 61 is in the position shown in Fig. 13, the feed cylinder bore at the front'side of the feed piston may be connected to exhaust through ports 98, the interior of the feed piston rod, passages, 91, 96, groove 9|, ports in the valve bushing, exhaust chamber 85, passage 86, the exhaust groove 81 and exhaust passages 88 and 89. Also when the control valve 61 is in the position shown in Fig. 13, the feed cylinder bore at the rear side of the feed piston may be connected to exhaust through the tube |04, recess |03, passages |02, IOI, past the automatic torquecontrolled valve means |00 and through passage vsure through the forward 99, chamber 92, the ports in the valve bushing, valve exhaust chamber 93, passage gli and exhaust passages t8 and i3d. When the valve Kill lsin the position shown in Fig. l2 the reverse feed passages are connected to the supply groove and when the valve is shifted forwardly from the posi-1 tion shown in Fig. 13 the forward ieed supplyy chamber may be connected te the supply groove. This valve will hereinafter be described more i'ully. Tt will thus be seen that under the control of the control valve ai, liquid under pre sure may be supplied to the feed cylinder bore ai either side of the feed piston to effect forward or reverse ieed as desired, and the manner in which the forward feed is influenced by the automatic torque-controlled valve means it@ will now be described.

The torque on the bit rotating motor ll@ automatically regulates the flow of liquid under presfeed passages under the control of the torque-controlled valve means |90 above referred to, in a manner similar to that described in the copending application Ser. No. 268,792 above referred to, and in the present invention the torque-controlled valve means has a further, venting, function whereby the forward feeding pressure may be vented when the torque on the bit rotating motor 40 exceeds a predetermined amount. The special utility of this feature will be shortly described. As previously described, the stator casing of the bit rotating motor 40 has limited rotation relative to the control head 35, and secured to the end plate 52 is a torque pin |05 (Figs. 1 and 7) engageable in a groove i@ in a reciprocable valve tappet |91. Tightly pressed in a transverse bore it in the control head 35 is a valve sleeve it@ having a conical valve seat Il@ with which a sleeve valve iii is engageable. A valve stem M2 integral with the tappet ii has a tight sliding t with the valve li i and the valve is yieldingly held against a shoulder i i3 on the valve stem by a coil spring iid. The valve l i i vhas an internal annular groove H5 connected by ports i iii with a chamber H1 which surrounds the valve. Formed in the valve stem is an axial passage ||8 communicable through ports H9 with the internal groove ||5 in the Valve iii in some positions of the latter relative to the stem, but

normally sealed by the inner wall of the hollow valve. When the sleeve valve ill is against the shoulder H3, as shown in Fig. 9, communication of the ports ||9 with the groove ||5 is cut off by the body of the sleeve valve, while when the parts are in the position shown in Fig. 10 the ports I |9 are in communication with the groove ||5. The valve sleeve is transversely slotted at |20, and this slot is connected by a port 2| with the chamber |1. The opposite side of the valve sleeve is transversely slotted at |22, and this slot is connected by a port |23 with an enlarged bore |24, the latter being communicable under the control of the valve I with the chamber ||1. The passage 99 communicates with the slot |22 and the slot |20 communicates with the forward feed passage |0|. As shown in Fig. 10, a longitudinal groove |25 on the exterior of the valve sleeve connects a chamber |26 at the outer end of the valve sleeve bore with a transverse slot |21 which is connected by passages |28 and |29 with the exhaust groove 81 which is in turn connected to exhaust through passages 88 and 89 as previously explained. The valve stem ||2 has a sliding fit with the valve sleeve bore, and packings |30 sealingly engage the valve stem to agees/ia reduce the possibility of leakage. Any leakage of liquid along the valve stem. may iiow from the packing bore to the slot l2?, as shown in Fig. l0. Threaded within one end oi the val e sleeve bore iisd is closure plug i while threaded within the opposite end ci the valve sleeve bore is a plug and interposed between the latter plug and the valve tappet 21 is coil spring i3@ which. constantly urges the tappet toward the right as viewed in i 7. The coil spring is arranged 'dahin a bore i3d in the 32, and the tappet is guided in this bore in the manner shown. Ttfnen the tappet is in the position shown in Figs. 4': and 1 it may abut at its right hand end with the inner end of the valve sleeve lila, and when the tappet is in its extreme left hand position it may abut a shoulder 35 on the plug |132. The pressure exerted by the spring Mii on the stem iii? when the valve is seated is opposite to the direction in which the pin |05 tends to move the tappet |01 as a result of the torque reaction of the bit rotating motor dii, and the pressure exerted by the spring |33 is sufiicient to hold the motor stator against rotation during normal full load drilling torque. The spring iid is made of such strength that it will not yield and permit movement of the stem M2' relative to the valve il I, with resultant communication of passages H9 with groove H5, until a denite overloading of the motor occurs. The spring is preferably made about one quarter as strong as the main spring |33, plus an amount sufficient to oiset the force due to the hydraulic pressure acting on the difference between the areas of the valve and valve stem. Noting that additional compression oi the spring |33 will also have to be effected as overload increases, it will be apparent that a material overload, in excess by desirably upwards of 25% of normal full load, will be necessary on the motor before space |29 will be connected to vent. Now, it will be noted that if the load on the bit rotating motor exceeds a predetermined amount, i. e., if the resistance to motor rotation becomes excessive, the motor stator rotates slightly relative to the control head 35, thereby moving the torque pin i635 and valve tappet |01 to the left as viewed in Figs. 4 and 7, against the pressure of the spring |33; and as a result the valve I il is moved toward its seat or completely seated, thereby partially to close or completely to cut off the flow of liquid under pressure from the passage il@ to the forward feed passage |0|. If the load on the bit rotating motor becomes even greater (which it may do despite the interruption of admission of feeding uid, as will shortly be explained), i. e., if the resistance to motor rotation exceeds that which was previously predetermined as sullcient to warrant interruption ot feeding, the' motor stator will rotate slightly further relative to the control head, thereby moving the torque pin and valve tappet further towards the left, moving the valve stem relative to the seated valve from the position shown in Fig. 9 into the position shown in Fig. 10, and as a result the forward feed passage |0| is vented through slot |20, port |2I, chamber ||1, the ports ||6 and groove ||5 in the valve ports ||9 and passage ||8 in the valve stem, the chamber |26, groove |25, slot |21 and passages |28 and |29, groove 81 and exhaust passages 88 and 89. It is accordingly evident that variations in the load on the motor, due ordinarily to variations in the pressure with which the bit is forced to work, will automatically effect control of the flow of fluid relative to the space at the rear end of the feed cylinder and interrupt supply to this space as overload of sufficient degree occurs, and on still greater overload vent this space. It will be observed also that the leftward movement of the valve stem I2 beyond maximum venting position will, with the proportions shown, be precluded.

Again referring to the control valve 51, it will be noted that the same has spaced heads carrying packln'g rings and separated by grooves |40 and |4I, the latter being. of substantially greater width than the former. The valve has an axial chamber |42 and an end recess |43, and the groove |40 is connected with the chamber |42 through a series of ports |44 while the wide groove I4| is connected with the chamber |42 through a series of radial ports |45. Series of radial ports |45, |41 and |48 in the valve bushing connect the valve bushing bore respectively with the chamber 82 and grooves 90 and 9|. When the valve is in the position shown in Fig. l2, the groove |4| connects the reverse feed groove 9| with the supply groove 80 so that liquid under pressure may flow from the supply chamber to the front end of the feed cylinder bore at the forward side of the feed piston. When the valve is in the position shown in Fig. 13, the feed cylinder bore at the forward side of the feed piston is connected to exhaust through the groove 9|, ports |48, past the outer face of the rear valve head and through the valve bushing bore to the exhaust chamber 85. Concurrently, the feed cylinder bore at the rearward side of the feed piston is connected to exhaust through the chamber 82, ports4|46 and ports |48 in the valve. When the valve is moved into its extreme position to the left from that shown in Fig. 13, the groove |40 connects the chamber 82 with the supply groove 80, so that pressure fluid may be supplied at that time to the forward feed passages while the reverse feed passages are connected to exhaust through groove 8| and exhaust chamber 85. The other positions of the control valve and its other functions are clearly described in the copending application above referred to. Arranged in one of a pair of alined bores (Fig. 4) extending transversely and at opposite sides of the control head 35 is a manual control valve |52 which is adapted to control the flow of liquid under pressure to one side of a diaphragm |53 (Figs. l, 6 and 18) which controls the actuation of the motor control switch 55 (Fig. l). Arranged in the other bore is a manual control valve |54 which controls the supply of liquid under pressure through the motor rotor shaft and rod line to the drill bit.I These control valves |52 `and |54 are likewise fully described in the copending application above ref erred to.

The general mode of operation of the improved drilling apparatus is as follows. The apparatus may be set up in proper operating position with respect to the working face with the swivel plate 5 of the trunnion support suitably clamped in a saddle mounting of a suitable support, such as a mine column. The rod line is coupled by the chuck 51 to the motor rotor shaft and the drill bit is coupled to the rod line in a well known manner. Assuming that a starting hole has been made (this can be done in any suitable manner) and that the drill is alined with this hole, the operator will then manipulate the control handle 8| of the control valve 61, moving the latter into a position to supply liquid under pressure to the bit rotating motor 40,

. tarily,

forward feed passages to effect forward movement of the feed piston 8 within the then stationary feed cylinder 8, thereby to feed the bit rotating motor forwardly to bring 'the drill bit within the starting hole at the working face against the bottom of the hole. Thereafter the control valve 81 is moved into a position to cut off flow of liquid under pressure to the forward feed passage, and, due to inherent leakage in the fluid line and the fact that a non-expansible fluid is used, the forward feeding pressure on the drill bit is reduced to a very low value substantially removing the feeding pressure from the drill bit. The operator may then adjust the control valve |54 to effect a supply of drilling liquid to the drill bit. Upon further manipulation of the control handle for the valve 61, the latter is moved into a position whereinliquid under pressure is supplied to the motor switch passages so that liquid pressure acts on the diaphragm |53 to actuate the motor switch 55 to start the and as a result the drill bit is rapidly rotated. Upon further manipulation of the control handle for the control valve 61, the latter is moved to a position to again supply liquid under pressure to the forward feed passages to effect forward movement of the feed piston within the then stationary feed cylinder to feed the bit rotating motor forwardly while the drill bit is rapidly rotated, thereby to effect drilling. The forward feeding pressure on the drill bit is sufficient to overload the bit rotating motor 40 in the event of any change in drilling conditions increasing above normal the torque requirements, and in the event of initiation of overloading of the motor, due to an excessive motor torque, the torque-controlled valve means |00 is actuated partially or completely to close the valve thereby to reduce or completely cut off the flow of liquid through the forward feed passages to slow down or stop forward feed and preclude serious overloading of the motor, and when the motor again operates at its normal load rating, forward feed is automatically resumed or brought back to its desired rate, as the case may be. Thus the actual feeding pressure on the drill bit will always be kept at, or near, as an upper limit, that required to keep the bit rotating motor 40 working at its normal load rating, although the feeding pressure may be obviously greatly reduced or even entirely removed if conditions of drilling increase in difficulty. It will be apparent that sharp increases in torque requirements will entirely interrupt feeding fluid supply momenand that slighter ones will serve to throttle the feeding fluid supply, and that depending on the pressure in the feed pressure supply line and the strength of the spring |33 the normal full load position of the valve may vary.

A very important feature of the present invention may now be noted. The bit rotating motor 40 may be fed manually simply by manipu- 'rating the hand crank 28 to rotate the feed screw tube 2| relative to the non-rotatable feed nurl 23, thereby to move the feed cylinder 8 forwardly in its guide bore on the trunnion support. And the feed cylinder-can be moved forward relative to the feed piston while drilling is uninterrupted. As is the case with my earlier invention, when the feed piston has reached its limit of forward feeding travel relative to the feed cylinder, the control valve B1 may be positioned to supply liqthe reverse feed passages the feed piston, and the be fed forwardly in its uid under pressure to to effect retraction of feed cylinder may then guide bore on the trunnion support into a new and manual feed is continued by further movefeeding position and thereafter forward feeding ment of the hand crank, the bit rotating motor movement of the feed piston under the actuation would be overloaded or stalled. The mechanism of liquid under pressure may be resumed. `Upon described enables the drill bit to be fed forretraction of the feed, the motor switch is 5 wardly the combined distances of travel of the automatically actuated upon initiation of liquid feed piston in the feed cylinder and the feed flow to the reverse feed passages to stop the bit cylinder relative to the trunnion support without rotating motor, thereby to stop rotation of the interrupting feed, thereby to enable reduction in drill bit during reverse feed, this being desirable the time consumed during drilling and eliminatto prevent possible damage tothe drill bit. Also l@ ing the necessity of the operators feeding the during reverse feed the manual control valve drill hit through a series of definite steps.

i152 may be manipulated to interrupt the flow of It is important to note that as the manual drilling liquid to the drill bit. also, if desired, feeding means is operated to advance the feed the bit rotating motor may .be fed either for= cylinder relative to the Working face at a rate Wardly or rearwardly solely hy the hand crank i5 helovv Vthe rate of penetration of the hit, oonof the feed screw wholly independently of the entrent manual and automatic feeding is posflow or" liquid under pressure tothe feed cylinder, sible, automatic feed, of course, at a l3nt we may new note the improved and novel relatively slow rate as the valve tit `will oe parrnooie of operation above nec-:ritiorieolL The lmtiallv closed. manual feed; ci the feed. cylin- ,oroved torque-controlled valve means tilt! conrder were be effected at a rate exactly prises means whereby it possible for the hit to the rate of penetration of the hit, liquid woald rotating motor d@ to he fed forwardly the neither enter nos be vented from the i'eec evline drilling operation without having to me t during such inea if manually cte-d valve out of forward feeding positief advance oi the feed cylinder exceeds f forward feeding the drill E; t on, the valve 'will acting on the rear pressure il he vented from iced ton, it is desired to feed the feed. c; wardly its guide bore relata nien support by means or the :feed screw, and so to move the ey relative 'to piston, the oper." to turn the hand crank of the ree to the feed cylinder at than the rate of penetration of drill bi at rate greater than the drilling :frate e This will obviously cause the nora.

holes may materie..u as:

feeding pressure on the er i oit te incr/eac he?" "eelt of? the likei relatively eine and and, as a result, the torque en the hit rotating fielitit will also be evident tl iinu motor toheeome eazoessive, so that tlietorquelllf @Til- GGC mlsll is provid-@Ci hav controlled valve means: would move to the left. et imi-reveil mee-lis for controlling the feeds my; @my 5mm the pgiegm Shgwy n Fgsim@ ing pressure. lt still further be evident that "i, it happened to be there, but past the posian improved 'torque-controlled valve means is tion of Fig. il perhaps to that of Fig. lil` i. e. enf DGV-G TESEO-HSW@ iBS-Cl Changes Oli the bit iciently not only to effect seating of the valve vlg mmm Weeb me feeC-g pressure iii but also to move the valve stem to the left mail il@ llmly Controlled in accordance relative to the seated valve, thereby to open with viewing degrees of resistance to drill mi; the vent ports in the valve stem, and as a. re- X'Oon, @mi @mbolg means for automatsuit the uid in the rear end of the feed cylinder CPJY "Venting h feeding fluid when the load can he forced out as heretofore described through; @u the b1@ mt'wtmg mOOl iS Caused to exceed ports H5, groove M5, ports HQ, bore Eid, etc. ii@ 95 pedee'mnedmult. It will also be evident rlhe venting of liquid from the feed end of the that b5" @he D'YOVSOH 0f the alimatic feedr oonrear cylinder at the rear side of the feed pis? Woning mes @mbdllg 2 Vellilng fU-UCOD, ton enables manual advancing of the feed cylmanual feeding 0f the dlll ai; subsal'ay any nder n its guide bore on the nmmon Support time during the drilling operation may be caused by means of the hand crank for the feed screw. dit t@ supersede the automatic feed thereby t0 f2- During this manual overloading of @he bit rg- Cilitt and eXpede feeding 0f the drill. It tating motor 40, the overload on the latter causes Worth noting, in par@ again, that under the conthe torque to exceed the combined tensions of 9F01 0f the apparatus described there may be thespringsj and |33 plus the liquid pressure automatically effected, vwith feed rate automaton the differential area of the valve and valve ically controlled by the torque-controlled valve, stem, thereby to cause the valve stem to move forward feeding due t0 regulated influx of feedaxially relative tothe then seated valve Ill, ing liquid int the feed cylinder, interruption of which permits the liquid trapped in the feed feed by Cutting 01T 0f further inuX of feedcylinder at the rear side of the feed piston to i118 liquid by the 0Iqlle-c0ntr011ed valve, 60mdischarge through the feed exhaust passages. bined manual and automatic feeding by operat- 'I'his venting function is at all times under torque i118 the manual feeding means to effect cylincontrol so that varied rates of venting, adapted del mvement at a rate less than the rate of to different rates of cylinder movement are obpenetration. manual feeding by advancing the tained, and if the feed exhaust passages are of feed Cylinder and piston at a rate equal t0 the sumcient capacity the speed at which the oprate oi' penetration with neither addition nor erator manually feeds the feed cylinder forwarddischarge Of liquid relative t0 the feed cylinly has no substantial effect on the load on the der, and manual feeding and concurrent collapse bit rotating motor. of course, after the feed of the forward feeding chamber provided by the cylinder has been advanced so that the'rear cylcylinder and piston, by moving the cylinder forinder head abuts the rear end of the feed piston. ward more rapidly than the rate of penetration,

the connection between the source of feeding fluid supply and the feed cylinder then being closed and the vent opened by the assumption of the torque-controlled valve mechanism 'of a position similar to the one shown in Fig. 10. And the possibility of changing from automatic to manual feed at any time during the former,

f appended claims.

What I claim as new and desire to secure by Letters Patent is:

l. In a drilling apparatus, the combination comprising a drilling motor, fluid actuated feeding means therefor, means associated with said uid actuated feeding means for manually feeding said motor, means automatically operative when a predetermined load on said motor is reached for automatically interrupting the flow of fluid to said feeding means and entrapping the feeding fluid therein, and associated means automatically responsive to an increased load on said motor due to increased loading of said motor by said manual feeding means for venting the previously entrapped feeding fluid while precluding the entry of further feeding fluid thereto.

2. In a drilling apparatus, the combination comprising a drilling motor, fluid actuated feeding means for said motor including a feed cylinder containing a reciprocable feed piston, means associated with said fluid actuated feeding means for manually feeding said motor and including means for feeding said feed cylinder into different feeding positions, means responsive to load changes on said motor for automatically controlling the flow of fluid under pressure to said fluid actuated feeding means, and associated means responsive to an increased load on said motor caused by manual feeding of said feed cylinder while the latter contains fluid by means of which a feeding pressure is exerted, for automatically venting such fluid at a rate to maintain forward feed While precluding excessive motor load increases.

3. In a drilling apparatus, the combination comprising a rotary drilling motor for rotating a drill bit, fluid actuated feeding means for feeding the drill bit toward the Work comprising relatively reciprocable cylinder and piston feeding elements, manual means associated with said fluid actuated feeding means for feeding said feeding elements into different feeding positions, means responsive to the resistance to rotation of the drill bit for automatically controlling the flow of fluid under pressure to said feeding means, and means responsive to an excessive resistance to rotation of the drill bit due to overloading thereof by said manual feeding means through said fluid actuated feeding means for venting said feeding means thereby to permit manual feeding of the drill bit during the drilling operation by pressure transmitted through said fluid actuated feeding means while said fluid actuated feeding means are maintained ready for automatic resumption of feeding.

4. In a drilling apparatus, the combination comprising a rotary drilling motor for rotating a drill bit, fluid actuated feeding means for feeding the drill bit toward the work comprising relatively reciprocable cylinder and piston feeding elements, manualmeans associated with said fluid actuated feeding means for feeding said feeding elements into different feeding positions, means responsive to the resistance to rotation of the drill bit for automatically controlling the flow of fluid under pressure to said feeding means, and means responsive to an excessive resistance to rotation of the drill bit due to overloading thereof by said manual feeding means for venting said feeding means thereby to permit manual feeding of the drill bit during the drilling operation while said fluid actuated feeding means are maintained ready for automatic resumption of feeding when manual feed is discontinued, the venting of fluid from said fluid actuated feeding means enabling the effecting of relative longitudinal movement between said cylinder and piston elements by Asaid manual feeding means while a forward feeding pressure is maintained in said fluid actuated feeding means.

5. In a drilling apparatus, the combination comprising an electric motor for rotating a drill bit to cause the same to effect a drilling operation by a boring action, fluid actuated means for feeding the drill bit toward the work, and means responsive to load changes on said electric motor within certain predetermined limits for variably throttling the flow of fluid under pressure to said feeding means and embodying means automatically operative when said load limit is exceeded by a `predetermined amount for venting the feeding pressure.

6. In a drilling apparatus, the combination comprising a rotary drilling motor of the high speed electric type having a stator and a rotor, fluid actuated feeding means for said motor comprising a feed cylinder containing a reciprocable feed piston, a support carried by the piston rod of said feed piston, means for mounting said motor on said support including means for journaling said stator for limited rotation with respect to said support, and -a torque-controlled Y valve means carried by said support and operated by rotary movement of said stator with respect to said support, said valve means responsive to torque changes on said motor within certain predetermined limits for regulating the flow of fluid under pressure to said feeding means and embodying means for venting the feeding pressure fluid when said torque limit is exceeded.

7. In a drilling apparatus, the combination comprising a drilling motor of the high speed electric type having a. stator and a rotor, fluid actuated feeding means for said motor comprising a feed cylinder containing a reciprocable feed piston and having reversible fluid supply connections, a guide on which said feed cylinder is guided for reciprocation, a support carried by the piston rod of said feed piston, means for mounting said motor on said support including means for journaling said motor stator for limited rotation with respect to said support, means associated with said fluid actuated feeding means for manually feeding said feed cylinder into different feeding positions relative to said guide, and controlling means including a torque-controlled valve means carried by said support and operated by rotary movement of said stator with respect to said support, said torque-controlled valve means being responsive to torque changes on said motor within certain predetermined limits for regulating the ow of fluid under pressure to said feeding means and embodying means for venting the feeding fluid when said torque limit ls exceeded by a predetermined amount, said venting function permitting manual feeding of said feed cylinder relative to said guide without reversal of the fluid supply connections for said uid actuated feeding means, the venting of feeding pressure permitting movement of said feed cylinder by said manual feeding means relative to said feed piston.

8. In a drilling apparatus, the combination comprising a rotary drilling motor, feeding means for said motor, and means responsive to torque changes on said motor for automatically regulating the feeding pressure and embodying means for venting the feeding pressure when the motor torque becomes excessive, said torque-responsive means including a valve tappet guided for axial movement, spring for opposing suon tappet movement, said tappet having valve stem provided with a shoulder, a sleeve valve surrounding said valve stem, a spring for yieldlngly holding said sleeve valve against said shoulder, said sleeve valve adapted to seat when said first mentioned spring is compressed by a predetermined spring load to interrupt the flow of feeding pressure to said feeding means, and valve stem adapted to slide relative to said seated sleeve valve when both of said springs are compressed when said predetermined spring load is exceeded to effect a venting function.

d. In a drilling apparatus, the combination comprising an electric motor for rotating a. drill bit to cause the same to effect a drilling operation by a boring action, fluid actuated feeding means for the drill oit including a feed cylinder containing a reciprocable feed piston, the latter having a piston rod by which said motor is supported, and means responsive to torque changes on said motor due to variations in load on the drill bit for automatically interrupting ow of duid to said feeding means and entrapping fluid therein and for thereafter venting the uid therefrom.

10. In combination, a drill rotating motor, expansible chamber, iiuid operated feeding means therefor, manual feeding means for feeding said expansible chamber feeding means to eect motor feed, motor torque controlled regulating means for said fluid operated feeding means, and motor torque controlled means operable upon creation of a predetermined pressure in said expansible chamber by operation of said manual feeding means for venting the expansible chamber feeding means.

11. In a feed controlling mechanism for a drill bit, a valve device comprising cooperating relatively movable valve parts movable concurrently to interrupt feeding fluid supply and thereafter movable one relative to the other to vent fluid previously supplied, and means controlled by variations in the resistance to drilling for automatically effecting such movements of said parts.

12. In a drilling apparatus, the combination comprising a rotary drill bit, a motor for rotating said drill bit, power operated means for feeding said drill bit, manually operated means for feeding said drill bit, said manually operated means being adapted to have its operation initiated while the power operated feed is taking place, and means whereby upon the development of an fili o automatically from increased resistance to bit rotation under the action of said manually operated means automatic interruption of operation of said power operated feeding means is effected, said power operated feeding means during such interruption being maintained ready for automatic resumption of feeding on the resistance to drilling d ecreasing to a predetermined extent by the discontinuation of manual feed, said means whereby automatic interruption of operation of said power operated feeding means is elected comprising feed control means which is adapted to effect such interruption of operation of said power operated feeding means by venting the feeding pressure.

i3. In a drilling apparatus, the combination comprising a drill bit, a motor for actuating said drill bit to cause the same to effect a drilling operation, said motor including an element which provides the reaction necessary for the actuation of said drill bit, a motor support on which said reaction element is mounted for limited movement, means by which said reaction element is normally held against such relative movement While yet adapted when said motor is overloaded to move relative to said support, feeding' means for applying a feed pressure to said drill 'oit and means for controlling the operation of said feedrneans, said feed control means being adapted to operate automatically in accordance with variations in the resistance to drilling to preclude application of feeding pressures in excess of desired values to said drill bit, said feed control also including means tor automatically venting feeding pressure when the resistance to drilling is above a certain amount, said motor reaction element being movable relative to said support to effect said feed control.

A drilling apparatus as claimed in claim 13, characterized in that the element of said motor which provides the reaction necessary for the actuation of said drill bit is mounted on said motor support for limited rotary movement relative thereto and is normally held against said relative rotary movement but is adapted when overloaded to rotate relative to said support and thereby to effect said feed control.

l5. in a drilling apparatus, the combination comprising a drill bit, means for causing said drill bit to drill a .hole including feeding means operative upon the supply of operating medium thereto to apply a feeding pressure to the drill bit, and controlling means automatically controlled by changes in the resistance to drilling for precluding the application by operation of said feeding means by operating medium supplied thereto of a feeding pressure in excess of a desired value to the drill bit, said controlling means including a reaction member which moves a normal position upon the resistance to drilling exceeding a predetermined value, said controlling means being actuated, in a direction to preclude such an undesired application of feeding pressure, by movement consequent upon a predetermined resistance to drilling of said reaction member, said controlling means including a torque-controlled valve means responsive to variations in resistance to drilling for automatically precluding feeding pressures in excess of desired values by diminishing or interrupting the supply of operating medium to said feeding means and for automatically venting the feeding pressure when the resistance to drilling is above a certain amount.

16. In a drilling apparatus, the combination operated means for feeding said drill bit, said manually operated means being adapted to have its operation initiated while the fluid actuated feed is taking place, means whereby upon the development of an increased resistance to bit rotation under the action of said manually oper- .ated means automatic interruption of operation of said fluid actuated means is effected, said fluid actuated means during such interruption being maintained ready for automatic resumption of feeding on the resistance to drilling decreasing to a predetermined extent as for instance by the discontinuation of manual feed,

and feed controlling means whereby automatic interruption of said fluid actuated means is effected, said feed controlling means being adapted to effect such interruption of said fluid actuated feeding means by venting the fluid therefrom, said venting of fluid from said feeding means being adapted to enable relative longitudinal movement between said cylinder and piston elements by said manually operated feeding means.

17. In a drilling apparatus, the combination comprising a drillA bit, means for causing said drill bit to drill a hole including feeding means operative upon the supply of operating medium thereto to apply a feeding pressure to the drill bit, and controlling means automatically controlled by changes in the resistance to drilling for precluding the application by operation of said feeding means by operating medium supplied thereto of a feeding pressure in excess of a desired value to the drill bit, said controlling means including a reaction member which moves automatically from a normal position upon the resistance to drilling exceeding a predetermined value, said controlling means being actuated, in a direction to preclude such an' undesired application of feeding pressure, by movement consequent upon a predetermined resistance to drilling of lsaid reaction member, said controlling means being operative to preclude such an undesired application of feeding pressure by interrupting the supply of operating medium to said feeding means and also embodying means for venting operating medium from said feeding means when said predetermined resistance to drilling is exceeded.

18. In a drilling apparatus, the combination comprising a drill bit, means for actuating said drill bit including a bit actuating motor, feeding means operative upon the supply of operating medium thereto to apply a feeding pressure to the drill bit, and controlling meansautomatically controlled'by changes in the resistance to drilling for precluding the application by operation of said feeding means by operating medium supplied thereto of a feeding pressure in excess of a desired value to the drill bit, said controlling means including a reaction member operatively associated with said bit actuating motor and which moves automatically from a normal position upon the resistance to drilling exceeding a predetermined value, said controlling means being actuated, in a direction to preclude such an undesired application of feeding pressure, by movement consequent upon a predetermined resistance to drilling of said reaction member, said controlling means being operative to preclude such an undesired application of feeding pressure by interrupting the supply of operating medium to said feeding means and also embodying means for venting operating medium from said feeding means when said predetermined resistance to drilling is exceeded.

19. A drilling apparatus as claimed in claim 17, characterized in that said reaction member is mounted on a support in said apparatus for limited movement with respect thereto, and is normally stationary with respect to said support and is moved relative thereto when the reslst- I l ance to drilling attains a predetermined value, thereby effecting said actuation of said feed controlling means.

20. AA drilling apparatus as claimed in claim 18, characterized in that said bit actuating motor Y comprises relatively movable parts of which-one operates the bit and of which the other comprises said reaction member, a supporting member being provided for said reaction member with respect to which it is movably mounted and with respect to which it is a pted to move when resistance to drilling atta a predetermined value, thereby effecting saidgactuation of said feed controlling means.

21. In a drilling apparatus, the combination' comprising an actuator fora drilling implement, power operated means for feeding the drilling implement, additional means for vfeeding. the drilling implement, said latter means being adapted to have its operation initiated while the power operated feed is taking place, and means whereby upon the development of an increased resistance to drilling under the action of said additional feeding means automatic interruption of operation of said power operated feeding means is effected, said power operated feeding means during such interruption being main@ tained ready for automatic resumption of feeding on the resistance to drilling decreasing to a predetermined extent by the discontinuation of feed by said additional feeding means, and feed control means whereby automatic interruption of said power operated feeding means is effected, said feed control means being adapted to effect such interruption of said power'operated feeding means by venting the feeding pressure.

22. yIn a drilling apparatus, the combination comprising a drill bit, a motor for actuating said drill bit, fluid operated means for feeding said drill bit,V mechanical operating means for feeding said drill bit, said mechanical means being adapted to have its operation initiated while the fluid operated feed is taking place, and means whereby upon the development of an increased resistance to drilling under the action of said mechanical operating means automatic inter vruption of said fluid operated means is effected,

said fluid operated means during such interruption being maintained ready for automatic resumption of feeding on the resistance to drilling decreasing to a predetermined extent by the discontinuation of feed by said mechanical means, and feed control means whereby automatic interruption of said fluid operated feeding means is e'ected, said feed control means being adapted to effect such interruption of said fluid operated feeding means by venting the fluid therefrom, said venting of the fluid enabling operation of said mechanical feeding means.

23. In a drilling apparatus, the combination comprising a drill bit, a motor for actuating said drill bit, feeding means for said drill bit operable on operating medium supply thereto for applying a feeding pressure to the drill bit, a device for controlling the supply of operating medium to said feeding means, means normally biasing said control device toward a supply eil'ectlng position,e.n element supported for movement under forces produced by resistance to drilling and adapted to move said control device under such forces in. an opposite direction to eifect interruption of the fluid supply and to effect venting of operating medium from said feeding means, said means normally biasing said control device toward its supply effecting position operative to hold said element stationary until until resistance to drilling attains a predetermined value.`

24. In a drilling apparatus, the combination comprising a drill bit, a motor for actuating said drill bit to cause the same to .eilect a drilling operation, said motor including a rotary element operatively connected to the drill bit for rotating the latter, and a relatively stationary element, means for supporting said relatively stationary element for yielding movement under forces produced during drilling and verying with the resistance to drilling. feeding means for the drill bit for applying a feeding pressure to the drill bit, and means for controlling the operation of said feeding means, said feed-controlling means including an element operatively connected with said relatively stationary element and movable by the latter when resistance to drilling attains a predetermined value in a direction to effect venting of the feeding pressure to preclude application of feeding pressures in excess of desired values to said drill bit, said feedcontrolling means being operativei-upon movement of said movable element to reduce the flow of operating medium to said feeding means and to vent the feeding pressure to preclude such an undesired application of feeding pressure.

25. In a drilling fapparatus, the combination comprising an actuator for a drilling implement, power operated means for feeding the drilling implement, manually operated means for feeding the drilling implement, said manually operated means being adapted to have yits operation initiated while the power operated feed is taking place, and means whereby upon the development of an increased resistance to drilling under the action of said manually operated means automatic interruption of operation of said power operated means is effected, said power operated means during such interruption being maintained ready for automatic resumption of feeding on the resistance to drilling decreasing to a predetermined extent as for instance by the discontinuation of manual feed. said means whereby automatic interruption of operation of said fected `comprising adapted to effect of said power operated feeding means by venting the feeding pressure.

26. In .a drilling apparatus, the combination comprising an actuator for a drilling implement, said actuator including an element which provides the reaction necessary for the actuation of the drilling'implement, means for mounting said reaction element for hunted relative movement, means for normally holding said reaction element against such relative movement but which when overloaded permits said reaction element to move relative to its mounting means, feeding means for applying a feeding pressure to the drilling implement, and means for controlling y the operation of said feeding means, said feed controlling means being adapted to operate automatically in accordance with variations in the resistance to drilling to preclude application of feeding pressures in excess of desired values to the drilling implement, said feed controlling means also including means for automatically venting the feeding pressure when the resistance to drilling is above a certain amount, said reaction element of said actuator adapted upon such movement relative to its mounting means to ei'- fect said feed control.

27. In a drilling apparatus, the combination comprising an actuator for a drilling implement, said actuator including an element which provides the reaction necessary for the actuation of the drilling implement, means for mounting said reaction element for limited rotary movement, means for normally holding said reaction element against such rotary movement but adapted when the actuator is overloaded to permit rotation of said element relative to its mounting means, feeding means for applying a feeding pressure to the drilling implement, and means for controlling the operation of said feeding means, said feed controlling means being adapted to operate automatically in accordance with variations in the resistance to drilling to preclude application of feeding pressures in excess of desired values to the drilling implement, said feed controlling means also including means for automatically venting the feeding pressure when the resistance to drilling is above a certain amount, said reaction element of said actuator adapted upon such rotary movement relative to its mounting means to effect such feed control.

WIN W. PAGET.

CERTIFIoAT-E 0F CORRECTION. patent No. 2,288,5h5. .rune 5o, 19142.

WIN W PAGET It is hereby certified'that error appears inthe printed specification ofthe above numbered patent `requiring correction as follows: Psge 6, first column, line 51, for the word "feed" rend -renr; line 52, for-rear first occurrence, read -feed; page T, first column, line 55, claim 2, strike out the Accxmnsfafter "exerted; page 10, fir'st column, line 9, claim 25, efter'devicef insert --away-r; line 11, strike out ".'until" first occurrence; line 21, oldi-mii., for verying" read --varying-- andthat thesaid vLetteren Patent should be read with this correction therein that the same v:any conform to the record of the casein the Patent Office'.

signed ma sealed this 20th any or october, A. D. 19h2.

l AHenry van Arsdale,

(Seel) v i Acting Commissione-r of'Petents. 

